Update version action

Stream: general

[Yaël Dillies]

https://github.com/leanprover-contrib/update-versions-action hasn't been updated in a year and a half. As a result, it is not compatible with Lean 4. For context, it contains the action that provided the <version number> branches in mathlib. @Rob Lewis, should we resuscitate it?

[Rob Lewis]

Nope. This was for the leanprover-contrib compatibility checking that is unmaintained and outdated.

[Yaël Dillies]

Is the plan for Reservoir to take over this version managing?

[Eric Wieser]

These branches were also used by leanproject to allow upgrading dependencies without upgrading the lean version itself.

[Eric Wieser]

lake still does this, but instead of picking a version of the library compatible with the current lean, it just picks an incompatible version without upgrading Lean!

[Yaël Dillies]

Ah great :upside_down: